Commonest cause of thunderclap headache: AIIMS 10; NIMHANS 14
First, the core concept here is that thunderclap headaches are sudden and severe, and they're often indicative of a serious underlying condition. The key here is to remember which conditions present this way. Subarachnoid hemorrhage (SAH) comes to mind immediately because it's a classic cause. The sudden bleeding into the subarachnoid space causes a rapid increase in intracranial pressure, leading to that "thunderclap" presentation.
Why is SAH the correct answer? Well, SAH typically presents with a sudden, severe headache, often described as the worst headache of life. It's usually due to aneurysmal rupture, and the rapid onset aligns with the sudden increase in pressure. Other causes like cerebral venous thrombosis or pituitary apoplexy are less common and have different presentations. For example, cerebral venous thrombosis might have associated focal neurological deficits or seizures, but the headache is usually progressive rather than abrupt.
Now, looking at the wrong options. Let's say option B is migraine. Migraines can be severe but typically have a gradual onset over minutes to hours, not the sudden "thunderclap" type. Option C might be cluster headaches, which are severe but have a more gradual onset and are often associated with autonomic symptoms. Option D could be something like meningitis, but that usually presents with fever and other meningeal signs, not just a sudden headache.
The clinical pearl here is that any thunderclap headache is a medical emergency. The student should remember that the first step is to rule out life-threatening causes like SAH. A non-contrast CT head is the initial imaging of choice, followed by lumbar puncture if CT is negative but suspicion remains.
Putting it all together, the correct answer is subarachnoid hemorrhage. The explanation needs to be concise, covering the core concept, why SAH is right, why others are wrong, and the key clinical point. Let me structure that into the required sections with the specified formatting.
**Core Concept:** Thunderclap headache is a sudden, severe headache reaching maximal intensity within minutes and is a red flag for life-threatening neurological emergencies. The most common cause is subarachnoid hemorrhage (SAH), often due to ruptured cerebral aneurysms.
**Why the Correct Answer is Right:** Subarachnoid hemorrhage (SAH) causes a thunderclap headache due to rapid blood accumulation in the subarachnoid space, increasing intracranial pressure and irritating meninges. Classic features include a "worst headache of my life" sensation, often with neck stiffness, photophobia, or altered mental status. Immediate diagnosis via non-contrast CT head is critical, as delayed treatment leads to high mortality.
**Why Each Wrong Option is Incorrect:**
**Option A:** Cerebral venous thrombosis may cause headache but typically presents with progressive, non-thunderclap pain, often with focal neurological deficits or seizures.
**Option B